The present invention relates to a tool holder connection arrangement for a modular tool holder device for a tool machine intended to work metals and other materials.
To meet the every growing demand for flexibility in tool machines with tool holder-changing and blocking devices and with mounts for connection to the machine nose, controlled by numerical control units, manufacturers have been compelled to build devices allowing for interchangeability of the means for the attachment of the tool holder to the machine, whatever its shape. It is also desirable to provide the possibility of varying the type of tool holder according to the required working (boring, milling, tapping) and to provide the possibility of modifying the dimensions of the tool holder, that is, diameter and length, in order to reach all the zones to be worked without altering the rigidity of the whole.
Italian patent 1,121,138 discloses an arrangement with a series of elements for a modular tool holder device. The arrangement is for the working, especially chip-cutting, of metals by a tool machine. The tool cutting machine comprises a plurality of adapters provided with a machine nose mount, a plurality of intermediate elements of different diameter and length and a plurality of tool holder heads. The coupling between any two adjacent elements is carried out by screwing a shank, having cylindrical intermediate portion and a threaded end portion, within an axial seat forming a cylindrical guide and provided with a corresponding threading, and with axial abutment of two flat surfaces of the two elements. Each element may possibly be provided with means for axially adjusting the abutment. Additionally, the diameter of the seat and the shank of a same element can be varied to make up a series of reducing adapters.
However, the chip cutting device works at very high speeds. This is made possible by the higher power available at the spindle of the most recent tool machines. These high speeds generate a work torque at the tool tip which exceeds the tightening torque developed by the friction between the flat contact surfaces of two contiguous elements and determined by the screwing of the shank threaded portion into the corresponding axial seat. This causes a further screwing of the joint and hinders or even prevents the screwing off of the joint upon the disassembly of the matched modular parts, thus altering the operating capacities of the whole unit.
It is also known from documents DE=3540109 and GB 2,127,124 to provide a joint for blocking an adapter and a tool holder one to the other. The joint of the first document utilizes a journal made up of two parts of different diameters, each part being provided with a threading, and the two threadings being of different pitch. The joint of the second document utilizes a journal of one diameter which is only provided with two threadings of different pitch. Moreover, the joint described in the documents uses a tongue or a pin for the torsional blocking between the adapter and the tool holder.
On the other hand, the two threadings do not seem capable of ensuring the axial irremovability and ensuring the fixed position of the tongue. Further, the pin is not able to change the relative orientation between the adapter and the tool holder. Moreover, the joints disclosed in the documents do not allow the fixing of the journal to the tool holder nor the passage of oil for cooling the tool.